Coatings

ABSTRACT

An ultra-high solids content primer coating composition comprising: (i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin; (ii) 1.5 to 12 wt % of at least one silane; (iii) 0 to 20 wt % of at least one hydrocarbon resin; (iv) 0 to 15 wt % of at least one reactive diluent; (v) at least one curing agent; wherein said composition has a solids content of at least 90 wt % according to ASTM D5201-05; wherein said composition has a viscosity of 200 to 800 cps at 23° C. and 50% RH (ASTM D4287); and wherein the ratio between hydrogen equivalents in the curing agent and epoxy equivalents of the coating composition is in the range 50:100 to 120:100.

This invention relates to a low solvent or solvent free epoxy primercoating composition that can be applied by conventional airless sprayequipment to provide a fast curing anti-corrosive primer layer on asubstrate. In particular, the primer can be a universal primer and canbe applied in a single coat without the need for over-coating.

In order to provide a coating composition capable of airless sprayingand having exceptionally low solvent content, the invention requires thecombination of a bisphenol F epoxy resin with a certain content ofsilane crosslinking agent and preferably a reactive diluent and ahydrocarbon resin.

BACKGROUND OF INVENTION

In conventional painting of ships, various parts of a ship areindividually coated with anticorrosive paints. A ship is built bymanufacturing individual blocks and assembling them, so that thepainting work needs to be carried out for each block before assembly.

A universal primer (single layer primer) typically having excellentweather resistance, adhesion to various finish coatings andanticorrosive properties is used to coat the blocks (which arepreviously subjected to surface treatment). This makes the paintingprocess simple and minimises waste.

Known universal primers include those based on an epoxy resin, a vinylchloride-based copolymer and a curing agent (JP211464/1998). Thiscoating composition, however, uses a solid epoxy resin and a solidamine-based curing agent and hence requires large amounts of solvent. Itis generally preferably to reduce solvent content for safety, economicand environmental reasons. A high solids universal primer is thereforesought.

As a high-solids epoxy-based anticorrosive paint that solves the aboveproblems, there has been developed an anticorrosive coating compositioncomprising a main agent component containing a liquid epoxy resin ofbisphenol A type and an amine-based curing agent that uses aliphaticpolyamine, alicyclic polyamine, aromatic polyamine, polyamide and thelike singly or in combination (for example, JP80563/2002). Thishigh-solids anticorrosion paint has a solids content of about 80% byweight and has a solvent content of about 20% by weight.

EP-A-1788048 describes a high-solids anticorrosive coating compositionthat cures rapidly. Whilst the document refers to a high solid contentof up to 100% many of the examples contain significant amounts ofsolvent such as benzyl alcohol which under new legislation is consideredto contribute to VOC. The coatings of the present invention have lowerVOC and can be applied with conventional airless spray equipment with auseful pot life of 1.5 hrs or more. The high solids examples 16-18 havevery poor pot life, possibly due to the excessive viscosity of theblend.

The present inventors have now devised a new high solids, universalprimer that out performs existing technology, in particular in terms ofserviceable pot life and flexibility. Not only therefore can thecomposition of the invention be applied over a much longer period butthe resulting coating is more flexible. Without wishing to be limited bytheory we surmise that both these effects are linked to the lowerviscosity we achieve in our invention compared to other high solidscoating compositions.

One of the main limitations of the service life of Universal Primers,such as those applied in water ballast tanks, is brittleness. As thesteel structure of the vessel moves due to strain from the environment(waves, wind, currents and temperature variations) there is a risk thatthe coating will crack, the welding seems, being the most sensitivearea.

The solvent free system of the invention has proven to be much moreflexible, which can be expected to contribute to significantly reducethe maintenance and repair work during which time the vessel is takenout of service.

Another weakness in these tanks is low DFT areas and the developedproduct has proven extremely good performance even at DFT's as low as160 micrometer.

The anticorrosive properties of the developed coating have also shown tobe exceptionally good. Several accelerated test methods has beenutilized to evaluate the anticorrosive properties of the developedproduct such as rust creep and disbondment of the coating from the steelsubstrate. All the testing carried out shows that a single coat of thenew solvent free epoxy is superior to two coats of existing universalprimer coatings when compared at the same total DFT (320 micrometer).

Overcoating intervals is another common challenge with solvent freesystems, as the maximum overcoating interval tends to be rather short.The current formulations offer recoating intervals up to 2 weeks underoutdoor exposure. This is the same level as existing solvent bornproducts and considered to be good for a solvent free system.

Another target of this development has been to develop a product thatcan be applied all year around with conventional airless spray equipmentand with a good pot life. In order to reach this goal much efforts hasbeen spend on decreasing viscosity whilst maintaining anticorrosiveproperties, a task that has been successfully completed at least for atemperature interval in the range between −5 and 40° C.

In addition it has been found that the current solvent free epoxycoating compositions offers excellent anticorrosive properties, long potlife and good drying time. In contrast, most solvent free systems showsignificantly increased drying times and a short pot-life.

SUMMARY OF INVENTION

Thus, viewed from one aspect the invention provides an ultra-high solidscontent primer coating composition comprising:

(i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0.5 to 20 wt % of at least one hydrocarbon resin;

(iv) 1.0 to 15 wt % at least one reactive diluent; and

(v) at least one curing agent;

-   -   wherein said composition has a solids content of at least 90 wt        % measured according to ASTM D5201-05;    -   wherein said composition has a viscosity of 200 to 800 cps at        23° C. and 50% RH (ASTM D4287); and    -   wherein the ratio between active hydrogen equivalents in the        curing agent and epoxy equivalents of the coating composition is        in the range 50:100 to 120:100.

Preferably, the coating composition has a solvent content of less than 5wt %.

Viewed from one aspect the invention provides an ultra-high solidscontent primer coating composition comprising:

(i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0.5 to 20 wt % of at least one hydrocarbon resin;

(iv) 0 to 15 wt % at least one reactive diluent; and

(v) at least one curing agent;

-   -   wherein said composition has a solids content of at least 90 wt        % measured according to ASTM D5201-05;    -   wherein said composition has a viscosity of 200 to 800 cps at        23° C. and 50% RH; and    -   wherein the ratio between active hydrogen equivalents in the        curing agent and epoxy equivalents of the coating composition is        in the range 50:100 to 120:100.

Viewed from another aspect the invention provides an ultra-high solidscontent primer coating composition comprising:

(i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0 to 20 wt % of at least one hydrocarbon resin;

(iv) 1.0 to 15 wt % at least one reactive diluent; and

(v) at least one curing agent;

-   -   wherein said composition has a solids content of at least 90 wt        % measured according to ASTM D5201-05;    -   wherein said composition has a viscosity of 200 to 800 cps at        23° C. and 50% RH (ASTM D4287); and    -   wherein the ratio between active hydrogen equivalents in the        curing agent and epoxy equivalents of the coating composition is        in the range 50:100 to 120:100.

Viewed from another aspect the invention provides an ultra-high solidscontent primer coating composition comprising:

(i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0 to 20 wt % of at least one hydrocarbon resin;

(iv) 0 to 15 wt % at least one reactive diluent; and

(v) at least one curing agent;

-   -   wherein said composition has a solids content of at least 90 wt        % measured according to ASTM D5201-05;    -   wherein said composition has a viscosity of 200 to 800 cps at        23° C. and 50% RH (ASTM D4287); and    -   wherein the ratio between active hydrogen equivalents in the        curing agent and epoxy equivalents of the coating composition is        in the range 50:100 to 120:100.

Viewed from another aspect the invention provides an ultra-high solidscontent primer coating composition comprising:

a component (A) comprising at least one bisphenol F epoxy resin; and

a component (B) comprising at least one curing agent;

said primer coating composition further comprising at least one silane,and optionally at least one hydrocarbon resin; and optionally at leastone reactive diluent;

wherein said coating composition comprises:

(i) 5.0 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0 to 20 wt %, such as 0.5 to 20 wt %, of at least one hydrocarbonresin;

(iv) 0 to 15 wt %, such as 1.0 to 15 wt %, of at least one reactivediluent;

wherein said composition has a solids content of at least 90 wt %;

wherein said composition has a viscosity of 200 to 800 cps at 23° C. and50% RH;

and wherein the ratio between active hydrogen equivalents in the curingagent and epoxy equivalents of the coating composition is in the range50:100 to 120:100.

Viewed from another aspect the invention provides a kit comprising:

a component (A) comprising at least one bisphenol F epoxy resin; and

a component (B) comprising at least one curing agent;

components (A) and (B) being suitable for blending prior to applicationof the resulting composition to a substrate:

wherein upon blending components (A) and (B) the resulting compositioncomprises:

(i) 10 to 50 wt % of at least one bisphenol F epoxy resin;

(ii) 1.5 to 12 wt % of at least one silane;

(iii) 0 to 20 wt %, such as 0.5 to 20 wt %, of at least one hydrocarbonresin;

(iv) 0 to 15 wt %, such as 1.0 to 15 wt %, of at least one reactivediluent;

wherein said composition has a solids content of at least 90 wt %;

wherein said composition has a viscosity of 200 to 800 cps at 23° C. and50% RH;

and wherein the ratio between hydrogen equivalents in the curing agentand epoxy equivalents of the coating composition is in the range 50:100to 120:100.

Viewed from another aspect the invention provides a kit comprising:

a component (A) comprising:

(i) 20 to 60 wt % of at least one bisphenol F epoxy resin;

(ii) 2.0 to 15 wt % of at least one silane;

(iii) 0.5 to 20 wt % of at least one hydrocarbon resin; and

(iv) 0 to 15 wt %, such as 1.0 to 15 wt %, of at least one reactivediluent;

and a component (B) comprising at least one curing agent.

Viewed from another aspect the invention provides a kit comprising:

a component (A) comprising:

(i) 20 to 60 wt % of at least one bisphenol F epoxy resin;

(ii) 2.0 to 15 wt % of at least one silane;

(iii) 0 to 20 wt % of at least one hydrocarbon resin; and

(iv) 1.0 to 15 wt % of at least one reactive diluent;

and a component (B) comprising at least one curing agent.

Viewed from another aspect the invention provides a kit comprising:

a component (A) comprising:

(i) 20 to 60 wt % of at least one bisphenol F epoxy resin;

(ii) 2.0 to 15 wt % of at least one silane;

(iii) 0 to 20 wt % of at least one hydrocarbon resin; and

(iv) 0 to 15 wt %, such as 1.0 to 15 wt %, of at least one reactivediluent;

and a component (B) comprising at least one curing agent.

Viewed from another aspect the invention provides a substrate coatedwith a primer composition as herein before defined.

Viewed from another aspect the invention provides a substrate coatedwith a primer coating composition as herein before defined which hasbeen cured.

Viewed from another aspect the invention provides a process for thepreparation of a coating composition as herein before defined comprisingblending components (A) and (B).

Viewed from another aspect the invention provides a process for theapplication of a coating composition to a substrate comprising blendingcomponents (A) and (B) to form a mixture and applying said mixture to asubstrate, e.g. by airless spraying and optionally allowing said coatingto cure.

Viewed from another aspect the invention provides a process forapplication of a coating composition to a substrate comprising (I)blending components (A) and (B) as hereinbefore defined to form amixture and applying said mixture to a substrate, e.g. by airlessspraying;

(II) before said mixture cures on said substrate, applying a secondcoating of said mixture onto the coated substrate;

optionally repeating step (II); and

(III) allowing the coating composition to cure.

In all embodiments it is preferred if the coating composition comprises1.0 to 15 wt % of at least one reactive diluent.

In all embodiments it is preferred if the coating composition comprises0.5 to 20 wt % of at least one hydrocarbon resin.

Definitions

The invention relates to a high solids primer coating composition. Theterm coating composition is used to define a composition formed from thecombination of the first composition (A) and the second composition (B).To prevent premature curing, the primer coating composition of theinvention is supplied in two parts, a first composition (A) comprisingthe epoxy resin and a second composition (B) comprising the curingagent. The other components of the composition are preferably present incomponent (A) but could also be added via component (B).

DETAILED DESCRIPTION OF INVENTION

This invention relates to an anti-corrosive primer coating compositionfor a substrate such as a metal substrate especially a steel substrate.That steel substrate can be present on any object on which the coatingof the invention might be useful. In particular, the substrate is onewhich is exposed to the elements, such as wind, rain, ice or snow or isone which is exposed to water, especially sea water. The substrate maybe on an off-shore platform, wind turbine, chimney, power station orother industrial unit, bridge, crane, ship, vehicle and so on. Importantareas include void spaces, deck, super structures outside hull splashzones on off-shore installations and general outsides on offshoreinstallations where a long service life is required.

In a most preferred embodiment the substrate is part of a ship, inparticular the water ballast tank or potable water tank of a ship.

The primer coating composition forms an epoxy primer layer on thesubstrate. That primer layer can be overcoated as desired althoughideally the composition of the invention is a universal primer. Theuniversal primer provides good anticorrosive protection. If additionalantifouling properties, color stability or UV resistance is required anovercoating can be applied.

In a preferred embodiment primer coating composition is applied as asingle layer and is not overcoated. The nature of any overcoating layeris not a feature of this invention and hence any known overcoating layermay be used. Alternatively, the primer layer may be the only layerpresent in the substrate. Note that it is preferred if the coatingcomposition is applied as a single coat, i.e. in one application step.There is no need to apply the primer composition in multiple coatstherefore.

Primer Coating Composition

The primer layer coating composition comprises a binder based on atleast one epoxy resin. The combination of epoxy resins within the primerlayer composition is called a binder herein. Shortly before applicationof the primer layer composition to a substrate, the first composition ismixed with a second composition comprising a curing agent to form theprimer layer composition. That primer layer composition then cures onthe substrate to form the primer layer.

The binder in the primer layer composition may comprise one or more thanone epoxy resins. Ideally, the primer layer composition comprises atleast one liquid epoxy resin. The term liquid refers to the state of theepoxy resin at room temperature and pressure of 23° C., 1 atm.

A particular feature of the coating system of the invention is the highsolids content and thereby the low content of volatile organic compounds(VOC) present. The primer layer coating composition preferably has asolids content of at least 90 wt %, such as at least 95 wt %, morepreferably at least 99 wt %.

A particular feature of the coating system of the invention is the highvolume solids % (“VS %”) and thereby the low content of volatile organiccompounds (VOC) present. The primer layer coating composition preferablyhas a volume solids % of at least 90%, such as at least 95%, morepreferably at least 99%, especially 100%.

The first composition preferably has a volume solids % of at least 80%,such as at least 90% as well. The second composition preferably has avolume solids % of at least 80%, such as at least 90% as well.

The volume solids (expressed in %) is often referred to as “VS %”. VS %is determined according to D5201-05.

The primer composition of the invention contains a very low solventcontent such as less than 5 wt % solvent, especially less than 2 wt %solvent, more especially less than 1.0 wt % solvent, e.g. 0.5 wt % orless. Ideally there is no solvent present at all in our high solidscoating composition.

The first composition may also contain very low levels of solvent suchas less than 5.0 wt % solvent, especially less than 2.0 wt % solvent,more especially less than 1.0 wt % solvent, e.g. 0.5 wt % or less.Ideally there is no solvent present at all in the first composition. Thesecond composition may also contain very low levels of solvent such asless than 5.0 wt % solvent, especially less than 2.0 wt % solvent, moreespecially less than 1.0 wt % solvent, e.g. 0.5 wt % or less. Ideallythere is no solvent present at all in the second composition.

The high solids volume and low solvent content leads to lower VOCcontent. The VOC content is preferably less than 250 g/L, morepreferably less than 100 g/L, most preferably less than 50 g/L. In someembodiments the VOC content might be 25 g/L or less, such as 10 g/L orless. In this regard, volatile organic compounds include benzyl alcohol.

The very low content of VOC renders it possible to establish a fastcuring coating system which has a very short “T2” time (i.e. tack freetime), and a very short “T3” time (hard dry) time. The T2 time may beless than 20 hrs, such as less than 17 hrs. The T3 time may be less than24 hours (ASTM D5895 measured at 50% RH at 10° C. on a 350 micron filmthickness coating). In certain preferred embodiments, the “T2” time isless than 12 hrs hours at 23° C./50% RH. T3 time under the sameconditions may be 14 hrs or less such as 12 hrs or less.

The pot life of the coating composition of the invention is preferablyat least 1 hr, such as 1 to 3 hrs, e.g. 1.5 to 2.5 hrs. By pot life ismeant the time after mixing of the first and second components when thecomposition is still able to be applied to the substrate by an airlessspray procedure. If the composition cures too rapidly the coatingcomposition has a very short pot life. Pot lives of less than 30 minsare commercially challenging given the time it takes to coat a largeobject such as a ship block and the volumes of houses up to 150 mfeeding the spray gun.

Many of the important properties of the composition of the invention area consequence of the high solids and yet relative low viscosity of theclaimed composition.

The viscosity of the coating composition measured just after combinationof the two components can be in the range of 80 to 130 KU, such as 90 to120 KU (at 5° C.) or 60 to 105 KU, such as 70 to 100 KU at 23° C.

Alternatively viewed, the viscosity measured just after combination ofthe two components may be 200 to 800 cps, such as 200 to 700 cps at 23°C., especially 250 to 600 cps.

The viscosity of the first composition can be in the range of 300 to 800cps, such as 350 to 750 cps at 23° C.

It will be appreciated that the composition cures over time and hencethe viscosity of the composition increases during curing. The viscositymeasured in claim 1 is taken immediately after mixing and hence beforeany significant degree of the curing process has taken place. Byimmediately after mixing means within 5-10 mins of mixing.

Epoxy Resin

The epoxy-based binder system comprises one or more bisphenol F epoxyresins. The use of multiple epoxy groups in that resin (i.e. at least 2such groups) ensures that a cross-linked network can form.

The bisphenol F epoxy resin of the primer composition may have an EEWvalue of 100 to 350. However, it is particularly preferred if the FEW ofan epoxy resin of the primer layer composition is 300 or less such as100 to 300, especially 150 to 250, especially 170-200. Ideally, theepoxy resin is a liquid.

This level of EEW is important as it enables the preparation of a primerlayer composition having a desirable mixing ratio (e.g. 1:1 to 4:1, suchas 3:1 vol solids) between epoxy resin component (first composition A)and curing agent component (second composition B).

Also, it is well known that low Mw (often correlated with low EEW)resins have lower viscosity thus demanding less solvent for formulation.That reduces VOC content and enables the high solids content of theinvention. Care must be taken however that Mw is not too low as there isa risk of crystallisation if Mw is too low.

The Mw of the bisphenol F resin may be more than 170 g/mol.

A preferred bipshenol F (4′,4′-methylenebisphenol) resin derives fromthe combination of bisphenol F and epichlorohydrin. The use ofdifunctional resins is especially preferred.

The use of bisphenol F resins is important as these have been found toreduce the viscosity of the coating composition relative to coatingcompositions which comprise the more common bisphenol A resins.

It is possible to use a mixture of one or more epoxy resins, such as twoliquid epoxy resins. Thus, two type bisphenol F resins might beemployed.

These resins are readily available commercial products such as YDF-170(Kukdo), GY285 (Huntsman), DER354 (Dow), EPIKOTE 862 (Momentive),BFE-170 (CCP), or KF8100 (Kolon).

As well as the bisphenol F group, the composition may contain additionalepoxy resins selected from aromatic or non-aromatic epoxy resins,containing one or more epoxy group per molecule, which is placedinternally, terminally, or on a cyclic structure.

Suitable additional epoxy-based binder systems include epoxy andmodified epoxy resins selected from bisphenol A, Novolac epoxies, dimermodified epoxy, cycloaliphatic epoxies, glycidyl esters and epoxyfunctional acrylics or any combinations thereof.

Solid Epoxy

In a further preferred embodiment, a liquid epoxy primer is combinedwith a semi-solid or a solid epoxy resin in the binder composition. Thecombination of solid and liquid epoxy resins may lead to an idealdrying/curing time, whilst minimising VOC. By adding solid and liquidepoxy resins, we can reduce solvent and we therefore offer an idealbalance between drying/curing time, ease of handling and VOCrequirements.

The solid epoxy resin contains one or more epoxy groups. Suitableepoxy-based binder systems are believed to include epoxy and modifiedepoxy resins selected from bisphenol A, Novolac epoxies, non-aromatichydrogenated epoxies, dimer modified epoxies, cycloaliphatic epoxies,glycidyl esters and epoxy functional acrylics or any combinationsthereof.

Preferred solid epoxy resins include bisphenol A based resins, such as4,4′-isopropylidenediphenol-epichlorohydrin resins, novolac resins, andso on.

Most preferred are solid epoxy resins with an equivalent epoxy weight(EEW) of 300-1000. It is most preferred however if the EEW of the solidepoxy resin is in the range of 350 to 750, such as 400 to 700,especially 500 to 670. The use of a bisphenol A type resin is mostpreferred.

Alternatively viewed, in a preferred embodiment at least one epoxy resincomponent has an EEW less than 300 and a second epoxy resin has an EEWmore than 300.

If there are both liquid and solid epoxy resins present in the binder ofthe primer layer, it is preferred if the liquid epoxy resin is in excessrelative to the solid epoxy resin. Typically, the weight ratio of liquidto solid epoxy resin is in the range of 2:1 to 1:1, such as 2:1 to 1.1:1in the binder.

It is however preferred if the primer layer composition and hence thefirst composition comprises liquid epoxy resins only.

As noted below, the primer layer composition will contain othercomponents in addition to the epoxy resins forming the binder component.The binder component preferably forms 10 to 50 wt % of the primer layercomposition, such as 10 to 40 wt %, especially 20 to 40 wt %, mostespecially 25 to 35 wt %.

The binder component preferably forms 25 to 70 wt % of the firstcomposition that makes up the primer layer composition, such as 25 to 60wt % of the first composition.

Silane

The coating composition of the invention also contains at least onesilane. Silanes can improve drying properties at low temperature,flexibility, adhesion to substrates and anti-corrosive performance. Thesilane can be provided as part of the first composition or as part ofthe second composition, preferably the first composition. Ideally, thesilane is one that contains an epoxy group. Silanes of use in theinvention are generally of low Mw such as less than 400 g/mol. Suitablesilanes are of general formula (I) or (II)Y—R_((4-z))SiX_(z)  (I) orY—R_((3-y))R¹SiX_(y)  (II)

wherein z is an integer from 1 to 3,

wherein y is an integer from 1 to 2,

R is a hydrocarbonyl group having 1 to 12 C atoms optionally containingan ether or amino linker,

R¹ is a hydrocarbonyl group having 1 to 12 C atoms;

Y is a functional group bound to R that can react with correspondinghardener or binder functionalities and is preferably an amine or epoxygroup, and

each X independently represents a halogen group or an alkoxy group.

Preference is given to isocyanate, epoxy, amino, hydroxy, carboxy,acrylate, or methacrylate groups as functional groups Y. The Y group canbind to any part of the chain R. It will be appreciated that where Yrepresents an epoxy group then R will possess at least two carbon atomsto allow formation of the epoxide ring system.

It is especially preferred if Y is an amino group or epoxy group. Aminogroups are preferably NH₂. Y is preferably an epoxy group.

If the Y group is a polyamine and reacts with epoxy binder, it ispreferred if the silane is provided as part of the (B) component in thisscenario. In general, in the kit of the invention, the silane should notreact with any ingredient of the component of the kit in which thesilane is present.

It is especially preferred if X is an alkoxy group such as a C1-6 alkoxygroup, especially methoxy or ethoxy group. It is also especiallypreferred if there are two or three alkoxy groups present. Thus z isideally 2 or 3, especially 3. Subscript y is preferably 2.

R¹ is preferably C₁₋₄ alkyl such as methyl.

R is a hydrocarbonyl group having up to 12 carbon atoms. Byhydrocarbonyl is meant a group comprising C and H atoms only. It maycomprise an alkylene chain or a combination of an alkylene chain andrings such as phenyl or cyclohexyl rings. The term “optionallycontaining an ether or amino linker” implies that the carbon chain canbe interrupted by a —O— or —NH— group in the chain, e.g. to form asilane such as [3-(2,3-Epoxypropoxy)propyl]trimethoxysilane:H₂COCHCH₂OCH₂CH₂CH₂Si(OCH₃)₃ It is preferred if the group Y does notbind to a carbon atom which is bound to such a linker —O— or —NH—.

R might therefore represent (C₆H₅)—NH—(CH₂)₃— or Ph-NH—(CH₂)₃— or(C₆H₅)—(CH₂)₃ and so on.

R is preferably an unsubstituted (other than Y obviously), unbranchedalkyl chain having 2 to 8 C atoms optionally containing an ether oramino linker.

A preferred silane general formula is therefore of structure (III)Y′—R′_((4-z′))SiX′_(z′)  (III)wherein z′ is an integer from 2 to 3, R′ is a unsubstituted, unbranchedalkyl chain having 2 to 8 C atoms optionally containing an ether oramino linker, Y′ is an amino or epoxy functional group bound to the R′group, and X′ represents an alkoxy group.

Examples of such silanes are the many representatives of the productsmanufactured by Degussa in Rheinfelden and marketed under the brand nameof Dynasylan®D, the Silquest® silanes manufactured by OSi Specialties,and the GENOSIL® silanes manufactured by Wacker.

Specific examples include methacryloxypropyltrimethoxysilane (DynasylanMEMO, Silquest A-174NT), 3-mercaptopropyltri(m)ethoxysilane (DynasylanMTMO or 3201; Silquest A-189), 3-glycidoxypropyltrimethoxysilane(Dynasylan GLYMO, Silquest A-187), tris(3-trimethoxysilylpropyl)isocyanurate (Silquest Y-11597), gamma-mercaptopropyltrimethoxysilane(Silquest A-189), beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane(Silquest A-186), gamma-isocyanatopropyltrimethoxysilane (SilquestA-Link 35, Genosil GF40), (methacryloxymethyl)trimethoxysilane (GenosilXL 33), isocyanatomethyl)trimethoxysilane (Genosil XL 43),aminopropyltrimethoxysilane (Dynasylan AMMO; Silquest A-1110),aminopropyltriethoxysilane (Dynasylan AMEO) orN-(2-aminoethyl)-3-aminopropyltrimethoxysilane (Dynasylan DAMO, SilquestA-1120) or N-(2-aminoethyl)-3-aminopropyltriethoxysilane,triamino-functional trimethoxysilane (Silquest A-1130),bis(gamma-trimethoxysilylpropyl)amine (Silquest A-1170),N-ethyl-gamma-aminoisobytyltrimethoxysilane (Silquest A-Link 15),N-phenyl-gamma-aminopropyltrimethoxysilane (Silquest Y-9669),4-amino-3,3-dimethylbutyltrimethoxysilane (Silquest Y-11637),(N-cyclohexylaminomethyl)triethoxysilane (Genosil XL 926),(N-phenylaminomethyl)trimethoxysilane (Genosil XL 973), Deolink Epoxy TEand Deolink Amino TE (D.O.G Deutsche Oelfabrik) and mixtures thereof.

Other specific silanes of interest include 3-Aminopropyltriethoxysilane,3-Aminopropyltrimethoxysilane,N-(Aminoethyl)-aminopropyltrimethoxysilaneH₂NCH₂CH₂NHCH₂CH₂CH₂Si(OCH₃)₃, 3-aminopropylmethyldiethoxysilane,3-(2-aminoethylamino)propylmethyldimethoxysilane,(H₂NCH₂CH₂NHCH₂CH₂CH₂SiCH₃(OCH₃)₂),[3-(2,3-Epoxypropoxy)propyl]triethoxysilane(H₂COCHCH₂OCH₂CH₂CH₂Si(OCH₂CH₃)₃,[3-(2,3-Epoxypropoxy)propyl]trimethoxysilane(H₂COCHCH₂OCH₂CH₂CH₂Si(OCH₃)₃).

The use of silane GLYMO is especially preferred. A mixture of silanesmight also be used.

The amount of silane present in the first composition may be 2.0 to 15wt %, preferably 2.0 to 10 wt %, more preferably 2.0 to 8.0 wt % ontotal weight, ideally 2.0 to 7.0 wt %. The amount of silane in thecoating composition may be 1.5 to 12 wt %, preferably 1.5 to 8.0 wt %,more preferably 1.5 to 6.0 wt % on total weight, ideally 2.0 to 6.0 wt%. In general, silane is not present in the second composition. Theamount of silane in the combined composition is determined by the amountin the first composition taking into account the amount of secondcomposition then added. Increasing the silane content tends to decreasesthe viscosity of the composition. The combination therefore of thebisphenol F and the relatively high silane content (minimum 1.5 wt %)leads to a coating composition which has a remarkably low viscositygiven the very low level of solvent employed.

Reactive Diluent

The primer layer composition preferably further comprises a reactivediluent, preferably formed from a modified epoxy compound.

Examples of such reactive diluents include phenyl glycidyl ether, alkylglycidyl ether (number of carbon atoms in alkyl group: 1 to 16),glycidyl ester of versatic acid (R¹ R² R³ C—COO-Gly, where R¹ R² R³ arealkyl groups such as C8 to C10 alkyl and Gly is a glycidyl group),olefin epoxide (CH₃—(CH₂)n-Gly, wherein n=11 to 13, Gly: glycidylgroup), 1,6-hexanediol diglycidyl ether (Gly-O—(CH₂)₆—O-Gly), neopentylglycol diglycidyl ether (Gly-O—CH₂—C(CH₃)₂—CH₂—O-Gly),trimethylolpropane triglycidyl ether (CH₃—CH₂—C(CH₂—O-Gly)₃), andC1-20-alkylphenyl glycidyl ether (preferably C1-5 alkylphenylglycidylether), e.g., methylphenyl glycidyl ether, ethylphenyl glycidyl ether,propylphenyl glycidyl ether and glycidyl neodecanoate. Another preferredoption is Cardolite NC-513 derived from the reaction of epichlorohydrinand an oil obtained from the shells of cashew nuts.

Of the above reactive diluents, preferable are aliphatic reactivediluents such as 1,6-hexanediol diglycidyl ether or 1,4-butanedioldiglycidyl ether. Aliphatic glycidyl ethers of chain length 8 to 14 arealso preferred. The preferred reactive diluent will be aliphatic as itcontributes to the flexibility of the coating. The use of p-TBPGE isalso possible (para tertiary butyl phenyl glycidyl ether).

It is preferred if the reactive diluent is polyfunctional as opposed tomonofunctional as this speeds up the drying process and the increasedcrosslinking density. This also contributes to better anticorrosiveproperties.

The above reactive diluents can be used singly or in combination of twoor more diluents.

The reactive diluent is preferably present in the first compositionalong with the epoxy resin.

In the primer layer composition as a whole, the reactive diluent isdesirably contained in an amount of 0.5 to 20% by weight, preferably 1.0to 20% by weight, e.g. 1.0-15 wt %, especially 2.0 to 12 wt %.

In the first composition, the reactive diluent is desirably contained inan amount of 2.0 to 30% by weight, preferably 5.0 to 20% by weight, e.g.5.0 to 15 wt %, especially 6.0 to 12 wt %.

By adding the reactive diluent in the above amount, viscosity of themain primer layer composition is lowered to allow preparation of ahigh-solids composition.

Preferably the viscosity of the reactive diluent is <50 cP, preferably<30 cP, most preferably viscosity<20 cP at 23° C. and 50% RH Method iscone and plate viscometer according to ISO 2884-1:2006.

Hydrocarbon Resin

The coating composition of the invention may also comprise a hydrocarbonresin. This is preferably formulated as part of the first composition.In general, all types of hydrocarbon resin such as solid or liquid pureC5 and C9 hydrocarbon resins, mixtures of C5/C9, aliphatic/aromaticfeedstocks and modified type hydrocarbon resins with epoxy or hydroxylcan be utilized. The C5 resins are generally oligomers or polymers withfive carbons. The C9 resins are generally oligomers or polymers ofnine-carbon aromatic monomers. Preferably, the hydrocarbon resin has amolecular weight less than 1000 g/mol and most preferably molecularweight less than 500 g/mol.

In a most preferred embodiment, the hydrocarbon resin is a xyleneformaldehyde resin (such as EPODIL LV5).

Ideally, the hydrocarbon resin is a petroleum resin. The petroleum resinis a polymer that may contain a hydroxyl group, which is formed using,as a main raw material, a fraction produced as a by-product in thepetroleum refining, from petrochemical and carbon feedstocks.

Examples of the petroleum resins employable in the invention include anaromatic petroleum resin obtained by polymerizing a C9 fraction (e.g.styrene derivatives such as alpha methylstyrene, o,m,p-cresol, indene,methyl indene, cumene, napthalene or vinyltoluene) obtained from a heavyoil that is produced as a by-product by naphtha cracking, an aliphaticpetroleum resin obtained by polymerizing a C5 fraction such as1,3-pentadiene or isoprene, 2-methyl-2-butene, cyclopentadiene,dicyclopentadiene or cyclopentene. Also employable in the invention area copolymer-based petroleum resin obtained by copolymerizing the C9fraction and the C5 fraction, an aliphatic petroleum resin wherein apart of a conjugated diene of the C5 fraction such as cyclopentadiene or1,3-pentadiene is cyclic-polymerized, a resin obtained by hydrogenatingthe aromatic petroleum resin, and an alicyclic petroleum resin obtainedby polymerizing dicyclopentadiene. Mixtures of diaryl and triarylcompounds obtained from reaction of C9 blends under catalytic conditionsare also possible to utilize. Into these petroleum resins, hydroxylgroups are introduced. Of the above petroleum resins, a hydroxylgroup-containing aromatic petroleum resin is particularly preferablefrom the viewpoints of water resistance and seawater resistance.

Another possibly hydrocarbon resin is a xylene resin synthesized from1,3-dimethylbenzene and formaldehyde (e.g. Epodil LV5). Also employableare xylene resins modified with phenols such as bifunctional phenol(e.g., phenol, para-t-butylphenol, p-Cumylphenol, o,p-Dicumylphenol).

Another option is a coumarone resin which is a copolymer containing acoumarone constituent unit, an indene constituent unit and/or a styreneconstituent unit in its main chain.

The indene-coumarone resin may be modified with phenol at the end, andat least a part of aromatic rings in the coumarone resin may behydrogenated. Such coumarone resins include a liquid product having anumber-average molecular weight Mn (measured by GPC, in terms ofpolystyrene, the same shall apply hereinafter) of 200 to 300 and a solidproduct having a number-average molecular weight Mn of 600 to 800, andany one of them may be used singly, or both of them may be used incombination.

The use of solid hydrocarbon resins will generally be avoided.

Preferably the hydrocarbon resin forms 0.5-20 wt % of the coating,preferably 1.0 to 20% by weight, e.g. 1.0-15 wt %, especially 2.0 to 12wt %.

In the first composition, the hydrocarbon resin is desirably containedin an amount of 2.0 to 30% by weight, preferably 2.0 to 15% by weight,e.g. 3.0 to 10 wt %.

Most preferred is a hydrocarbon resin with an OH content of 0-5 wt % ora xylene formaldehyde with a OH content<3%.

It is also possible to utilize hydrocarbon resins based on hydrogenationof natural resins such as gum rosin, wood rosin and tall oil rosins.Hydrocarbon resins also based on esterification of rosin esters can beemployed.

Additives

The primer layer composition may also contain various other components,e.g. to enhance its anticorrosive properties. In particular, the primerlayer composition may comprise metal oxides, metal carbonates, talc,feldspar and so on to act as anti-corrosive materials. Specificanticorrosive functional pigments include zinc phosphate, zinc oxide,zinc dust, aluminium flakes, lead oxide. Zinc powder or zinc dust, whichis well known to incorporate in epoxy primer to produce a zinc epoxyprimer, is in this respect of special interest. Zinc powder or zinc dustcan all or partly be replaced by a zinc alloy, e.g. as disclosed in WO2008/125610. Auxiliary corrosion inhibitors, for example a molybdate,phosphate, tungstate or vanadate, ultrafine titanium dioxide, and/orzinc oxide and/or a filler such as silica, calcined clay, aluminasilicate, talc, barytes or mica.

The preferable filler package will comprise an extender with a low oilabsorption value such as BaSO₄, glass spheres, Feldspar, calcite,silica, aluminium oxide, zirconium oxide, dolomite, kaolin orwollastonite and optionally a laminar type of extender such as mica,talc, aluminium flakes, chlorite and china clay.

The primer layer composition or the first composition may comprise 30 to70 wt % of anticorrosive agents. Ideally these materials form more than45 wt % of the primer layer composition.

Other ingredients than the above various ingredients includeanti-sagging/anti-setting agent, plasticizer, inorganic or organicdehydrator (stabilizer), antifouling agent, colors and otherfilm-forming ingredients, can be added when needed.

As the anti-sagging/anti-setting agent (thixotropic agent), athixotropic agent, such as polyamide wax, polyethylene wax or abentonite-based thixotropic agent, may be employed. Examples of suchanti-sagging/anti-setting agents include Cryvallac Ultra, Crayvallac LV,both from Arkema, Thixatrol ST and Thixatrol Max, both from Elementis,Disparlon 6650 from Kusumoto Chemicals Ltd.

Examples of the color pigments include titanium white, red iron oxide,yellow iron oxide, carbon black and organic color pigments. Tinters maybe used to produce specific colours.

The total amount of the above-mentioned various additive componentsdepend upon the use and cannot be determined indiscriminately, but theyare frequently contained in the total amount of 10 to 65% by weight inthe first composition. Further, they are frequently contained in thetotal amount of 10 to 65 parts by weight in 100 parts by weight ofcoating composition.

Suitable solvents, if present, are hydrocarbons such as xylene. Solvent,if present, is preferably added to the first composition used to makethe primer layer composition. Some solvent might also be present withthe curing agent or in some of the additives used. The nature of thesolvent in the primer layer is not restricted, and publicly knownsolvents having boiling points of wide range are employable.

Examples of such solvents include xylene, toluene, MIBK,methoxypropanol, MEK, butyl acetate, benzyl alcohol, octyl phenol,resorcinol, n-butanol, isobutanol and isopropanol. The above solventscan be used singly or in combination of two or more kinds.

It is preferred however if no solvent is present at all.

Curing Agent

To allow curing of the first composition containing the epoxy binder, apolyamide, polyamine, epoxy-amine adduct, phenalkamine, or phenalkamidecuring agent may be used as is well known in the art. This may also beknown as a crosslinking agent or hardener. To function as a curingagent, the compound must contain at least two “reactive” hydrogen atomslinked to nitrogen. Thus the curing agent typically contains at leasttwo amines which may be primary or secondary.

Suitable curing agents are believed to include amines or aminofunctional polymers selected from aliphatic amines and polyaminescyclo-aliphatic amines and polyamines), polyamido amines, polyoxyalkylene amines (e.g. polyoxy alkylene diamines), aminated polyalkoxyethers (e.g. those sold commercially as “Jeffamines”), alkylene amines(e.g. alkylene diamines), aralkyl amines, aromatic amines, Mannich bases(e.g. those sold commercially as “phenalkamines”), amino functionalsilicones or silanes, and including epoxy adducts and derivativesthereof. Examples of suitable commercially available curing agents are:

-   -   Cardolite NC-541, ex Cardanol Chemicals (USA), Mannich base    -   Cardolite Lite 2001, ex Cardanol Chemicals (USA), Mannich base    -   Sunmide CX-105X, ex Sanwa Chemical Ind. Co. Ltd. (Singapore),        Mannich base    -   Epikure 3090 Curing Agent, ex Resolution Performance Products        (USA), polyamidoamine adduct with epoxy    -   Epikure 3140 Curing Agent, ex Resolution Performance Products        (USA), polyamidoamineEpikure 3115X-70 Curing Agent ex Resolution        Performance Products (USA), polyamidoamine    -   SIQ Amin 2015, ex SIQ Kunstharze GmbH (Germany), polyamidoamine    -   SIQ Amin 2030, ex SIQ Kunstharze GmbH (Germany), polyamidoamine    -   Polypox VH 40309/12, ex Ulf Prümmer Polymer-Chemie GmbH        (Germany), polyoxyalkylene amine    -   Polypox VH 40294, ex Ulf Prümmer Polymer-Chemie GmbH (Germany),        Mannich base    -   Ancamine 2609, ex Air Products (UK), Mannich base    -   Ancamine 2695, ex Air Products (UK), polyamine Ancamine 2738, ex        Air Products (UK), polyamine    -   Adeka Hardener, ex Adeka Corporation (Japan), Mannich base    -   API077, Admark, Mannich base    -   CeTePox 1490 H, ex CTP Chemicals and Technologies for Polymers        (Germany), poly oxyalkyl ene amine    -   Epoxy hardener MXDA, ex Mitsubishi Gas Chemical Company Inc        (USA), aralkyl amine    -   Diethylaminopropylamine, ex BASE (Germany), aliphatic amine    -   Gaskamine 240, ex Mitsubishi Gas Chemical Company Inc (USA),        aralkyl amine    -   Cardolite Lite 2002, ex Cardanol Chemicals (USA), Mannich base    -   Aradur 42 BD, ex Huntsman Advanced Materials (Germany),        cycloaliphatic amine    -   Isophorondiamin, ex BASF (Germany), cycloaliphatic amine    -   Crayamid E260 E90, ex Cray Valley (Italy), polyamidoamine adduct        with epoxy    -   Aradur 943 CH, ex Huntsman Advanced Materials (Switzerland),        alkylene amine adduct with epoxy

The use of modified polyamines is most preferred. Phenalkamines may alsobe used. It will be appreciated that the curing agent is shippedseparated from the epoxy resin and is only mixed with the epoxy resinshortly before application. The curing agent of the invention istherefore shipped as a second composition that is combined with thefirst composition to form the primer layer composition. The secondcomposition may consist of the curing agent.

A key parameter of the curing agent of interest is a viscosity below 300cP, such as 100 to 300 cP.

In a preferred embodiment, the curing agent is employed without the useof a separate catalyst to accelerate the crosslinking process. Someknown curing agents are however combined with a catalyst such as atertiary amine catalyst and that is within the scope of the invention.It will be appreciated that the curing agent can be supplied neat or ina solvent, ideally neat.

It is preferred if the epoxy-based binder systems that cure at ambienttemperatures.

The number of “active hydrogen equivalents” in relation to the one ormore curing agents is the sum of the contribution from each of the oneor more curing agents. The contribution from each of the one or morecuring agents to the active hydrogen equivalents is defined as grams ofthe curing agent divided by the active hydrogen equivalent weight of thecuring agent, where the active hydrogen equivalent weight of the curingagent is determined as: grams of the curing agent equivalent to 1 mol ofactive hydrogen. For adducts with epoxy resins the contribution of thereactants before adduction is used for the determination of the numberof “active hydrogen equivalents” in the complete epoxy-based bindersystem.

The number of “epoxy equivalents” is the sum of the contribution fromeach of the one or more epoxy resins and any other component thatcontains an epoxy such as the silane and reactive diluent. Thecontribution from each of the one or more epoxy resins to the epoxyequivalents is defined as grams of the epoxy resin divided by the epoxyequivalent weight of the epoxy resin, where the epoxy equivalent weightof the epoxy resin is determined as: grams of the epoxy resin equivalentto 1 mol of epoxy groups. For adducts with epoxy resins the contributionof the reactants before adductation is used for the determination of thenumber of “epoxy equivalents” in the epoxy-based binder system.

Preferably the ratio between the hydrogen equivalents of the totality ofthe curing agents and the totality of epoxy equivalents is in the rangeof 50:100 to 120:100.

Especially preferred epoxy-based coating compositions have a ratiobetween the active hydrogen equivalents of the curing agent and theepoxy equivalents of the composition in the range of 60:100 to 110:100such as 70:100 to 105:100, e.g. 80:100 to 90:100.

The mixing ratio of the first and second compositions is of coursegoverned by the relative amounts of epoxy and active hydrogens present.Ideally, the mixing ratio in solids volume is 1:1 to 10:1, first tosecond composition, such as 5:1 to 2:1.

Unless otherwise stated, all amounts stated as % by solids volume shouldbe understood as % by solids volume of the mixed primer layercomposition ready to be applied.

The curing agent composition (second composition) and first compositionare mixed shortly before application to the substrate.

Preparation of the Primer Composition

The primer composition may be prepared by any suitable technique that iscommonly used within the field of paint production. Thus, the variousconstituents may be mixed together using a high speed disperser, a ballmill, a pearl mill, a three-roll mill, an inline mixer etc. The paintsaccording to the invention may be filtered using bag filters, patronfilters, wire gap filters, wedge wire filters, metal edge filters, EGLMtumoclean filters (ex Cuno), DELTA strain filters (ex Cuno), and JenagStrainer filters (ex Jenag), or by vibration filtration.

The primer composition to be used herein are conveniently prepared bymixing the components. As an example, the first composition and thecuring agent component (the second composition) can be mixed by addingthe curing agent to the epoxy first composition and stirring well untilthe mixture is homogeneous. The mixture is immediately ready forapplication, e.g. by spray application, but may also be given aninduction time prior to application.

Application of the Primer Composition

The primer composition can be applied to a substrate (in particular asteel structure) by well-known standard application methods likeconventional air-spraying or by airless- or airmix-spraying equipment or2K airless spray pumps (or alternatively by means of a brush or aroller, in particular when used as a stripe coat). Preferably thecomposition is applied at ambient conditions without pre-heating thecoating composition. Conventional pressure such as 3 to 5 bars can beused.

Film Thickness

The coating is typically applied in a total dry film thickness of100-500 μm, such as 150-350 μm. It is preferred that the dry filmthickness of the primer layer is at least 100 μm. The applied filmthickness might vary depending on the nature of substrate being coatedand its predicted exposure scenario.

Curing

Once a substrate is coated with the coating, the coating must be cured.The primer layer may cure spontaneously. Whilst irradiation and heat maybe used to encourage curing, the compositions of the invention cure atambient temperature without further intervention.

Whilst it is preferred to apply a single coating, as the volatilecontent of the coating of the invention is so low, it is possible toapply a further coating whilst the primer layer is “wet”. There is norequirement therefore to wait for the first coating to cure beforeapplying a further coating. In order to build-up layer thickness, it isknown to apply multiple layers of the primer coating but conventionally,each layer is cured (dried) before a further layer is applied. In thepresent invention, application of further layers can be carried out on awet (or uncured) primer layer. This speeds up the application process.

In a further aspect therefore the invention includes a process in whichfurther coats of the primer layer coating composition are applied to anundercoat of the primer layer composition without an intermediate curingstep. Alternatively viewed, the invention includes a process in whichfurther coats of the primer layer coating composition are applied to anundercoat of the primer layer composition before the undercoat hascured.

The invention will now be described with reference to the following nonlimiting examples.

Analytical Methods

General procedure for preparation of the compositions

Component (I) of the primer layer was made by mixing all the indicatedingredients (in parts by weight) in a conventional manner known to theperson skilled in the art. Component (I) was then subsequently mixedwith Component (II)/Curing agent prior to application. The primer layeris typically applied by conventional airless spraying to a steelsubstrate.

Determination of Viscosity Using Cone and Plate Viscometer

The viscosity of the binders and paint compositions are determinedaccording to ISO 2884-1:2006 (ASTM D4287) using a Cone and Plateviscometer set at a temperature of 23° C. at 50% RH and providingviscosity measurement range of 0-10 P at 10000 s⁻¹.

The Stormer viscosity (KU) was carried out according to ASTM D 562 witha stormer viscometer at 23° C.

Determination of Drying Time by Beck and Koller (BK) Drying TimeRecorder

The applied films were exposed at 23° C./50% RH (or other condition asindicated) throughout the determination of the drying time. Beck Kollerdrying time was tested using the Beck and Koller drying time recorder inaccordance with ASTM D5895. T2—Tack free, T3—Hard dry time.

For this test, 300 microns DFT is used.

Determination of Pot Life

The pot life of the paints is determined by measuring the viscosityincrease directly after mixing of minimum 100 g of the paintcompositions at 23° C. The viscosity is measured according to ASTM D 562using a Stormer viscometer set at a temperature of 23° C. every 15minutes. The pot life is set to the time where the viscosity has reached110KU.

Elongation:

Conical mandrel bend test. Method is ASTM D 522.

On the conical panel (110×170×1T), each paint was applied with thicknessof 600 μm by applicator. Drying condition before bending is 4 weeks atambient temperature (23° C., 50% RH).

Determination of Dry Film Thickness (DFT)

Dry film thickness is measured using an Elcometer 456FBSI.

Determination of Solids Content of the Compositions

The solids content in the compositions are calculated in accordance withASTM D5201-05.

Calculation of the Volatile Organic Compound (VOC) Content of theCoating Compositions

The volatile organic compound (VOC) content of the coating compositionsis calculated in accordance with ASTM D5201-05.

EXAMPLES

In all example the ratio between active hydrogen equivalents in thecuring agent and epoxy equivalents of the coating composition is100:100. The calculated VOC of all these examples is 0 hence the solidscontent is 100%.

The following examples were prepared:

TABLE 1 Effect of epoxy resin First Comp. A ppw Recipe Recipe MaterialName EEW Recipe 1 C2* C3* BPF liquid epoxy Binder 172 30 BPA liquidepoxy Binder 190 30 BPA(n = 0) Binder 172 30 SILANE A-187 Binder 236 5 55 EPODIL LV5 Hydrocarbon 5 5 5 resin TiO₂ Universal Filler 10 10 10BaSO₄ Filler 39 39 39 Crayvallac Ultra Filler 1 1 1 NC-513 Reactive 49010 10 10 diluent Second Comp. B AHEW Modified Curing agent 95 100 100100 Polyamine AHEW 95 *comparative example

Stoichiometric amounts of the curing agent and binder are used.

Type of Epoxy Resin

1. BPF liquid epoxy: Bisphenol-F epoxy resin

2. BPA liquid epoxy: Bisphenol-A epoxy resin

3. BPA(n=0) epoxy: Bisphenol-A(n=0) epoxy resin

The viscosities of the resins are presented in table 2

TABLE 2 Recipe Recipe Recipe Recipe Recipe Recipe 5° C. 1 C2 C3 23° C. 1C2 C3 Viscosity KU * * ** KU 111 120.1 115.4 comp. A CPS 600 820 ** CPS620 800 620 Viscosity KU 106.5 115 ** KU 82.5 89.1 80.3 comp. A + CPS460 620 ** CPS 480 640 420 comp. B * not possible to measure becauseoutside the measureable region (>140 KU) ** not possible to measurebecause crystalized

The data shows that bisphenol F is the preferred option as it providesthe less viscous coating than recipe C2. The lower molecular weightBisphenol A of recipe C3 had a tendency to crystallize at lowtemperature.

Effect of Silane Coupling Agent

TABLE 3 Comp. A ppw Material Name EEW C4* C5* 6 7 8 9 C10 BPF liquid 17240 40 40 40 40 40 40 epoxy Silane A-187 236 0.5 2 4 6 8 10 EPODIL LV5 55 5 5 5 5 5 Crayvallac 1 1 1 1 1 1 1 Ultra TiO2 10 10 10 10 10 10 10Universal BaS04 38.5 37 35 33 31 29 39 NC-513 490 5 5 5 5 5 5 5 Comp. BAHEW Modified 95 100 100 100 100 100 100 99.5 Polyamine AHEW 95 SilaneAMEO 110 0.5

TABLE 4 Viscosity (CPS) at 23° C./50% RH - Results of varying content ofsilane coupling agents C4* C5* 6 7 8 9 C10* comp A >1000 >1000 975 780580 440 >1000 comp. A + B >1000 840 780 640 500 460 >1000

TABLE 5 Drying (50% RH) Comp A + B Drying time at 5° C./RH50% WFT: 350μm 5° C. C4 C5 6 7 8 9 C10 T2-Tack 20.1 18.4 18.8 17.1 19.9 18.7 18.4free time (hr) T3-Hard 31.6 29.5 27.6 26.2 23.9 23.4 28.6 dry (hr)

TABLE 6 Drying (50% RH) Comp A + B Drying time at 10° C./RH50% WFT: 350μm 10° C. C4 C5 6 7 8 9 C10 T2-Tack 14.1 14.1 13.8 13.2 12.4 11.5 15.2free time (hr) T3-Hard 20.1 18.8 17.3 16 15.2 14 22.3 dry (hr)

TABLE 7 23° C. C4 C5 6 7 8 9 C10 T2-Tack 9.4 9.1 8.3 7.9 7.4 7.1 7.5free time(hr) T3-Hard 11.8 11.5 9.9 10.7 9.4 9.4 10.2 dry (hr)

The silane coupling agents contribute to shorter drying times andincreasing levels have a more pronounced effect.

The drying times are a little longer than commonly used solvent bornUniversal Primers, but as a single coat system the total applicationtime of the system will be dramatically reduced.

Increasing amounts of Silane A-187 (epoxy functional silane) reduces theviscosity of the paint (See Recipes 4 to 9).

Effect of Epoxy Reactive Diluent

TABLE 8 Comp. A ppw Material Name EWW Recipe C11* Recipe 12 Recipe 13Recipe 14 Recipe 15 BPF liquid epoxy 172 40 30 30 30 30 1,6-HDDGE 150 10Neopentyl glycol 138 10 diglycidyl ether NC-513 490 10 p-TBPGE 225 10SILANE A-187 236 5 5 5 5 5 EPODIL LV5 5 5 5 5 5 TIO2 Universal 10 10 1010 10 BaSO4 39 39 39 39 39 Crayvallac Ultra 1 1 1 1 1 Comp. B AHEWModified 95 100 100 100 100 100 Polyamine AHEW 95 *comparative

TABLE 9 Viscosity (CPS) at 23° C./50% RH Recipe Recipe Recipe RecipeRecipe C11* 12 13 14 15 Comp. A >1000 460 500 615 560 comp. A + B 740360 380 480 420 *comparative

Aliphatic diluents are preferred as they contribute to the flexibilityof the coating. A difunctional reactive diluent will be preferred to amonofunctional as it speeds up the drying speed and the increasedcrosslinking density contributes to better anticorrosive properties.

TABLE 10 Elongation test C11 12 14 Elongation [%] Crack 15 19Pot life at 23° C./50% RH

TABLE 11 C11 12 13 14 15 Pot life [min] 90 90 105 135 135Effect of Hydrocarbon Resin

TABLE 12 Comp. A ppw Material Name EEW C16* 17 18 19 20 21 22 23 BPFliquid Epoxy 172 40 40 40 40 40 40 40 40 NC-513 490 5 5 5 5 5 5 5 5 TIO2Universal 10 10 10 10 10 10 10 10 BaSO4 39 34 32 29 34 34 34 34Crayvallac Ultra 1 1 1 1 1 1 1 1 SILANE A-187 236 5 5 5 5 5 5 5 5 EpodilLV5 0 5 7 10 Novares LC15 5 Novares LS500 Novares TL10 5 Novares LR600295 5 Enovik Albidur 300 5 EP 2240 Comp. B AHEW Modified Polyamine 95100 100 100 100 100 100 100 100 AHEW 95 *comparativeTypes of Hydrocarbon and Alternatives1. Epodil LV5: OH Content (0%), formaldehyde with 1,3-dimethylbenzene2. Novares LC15: OH Content (1.5%), phenol modified hydrocarbon3. Novares LS500: OH Content (7.3%), phenol modified hydrocarbon4. Novares TL10: OH Content (0%), C9 hydrocarbon5. Novares LR600: OH Content (0%), epoxy functionalized hydrocarbon,EEW=2956. Evonik Albidur EP2240: epoxy functionalized silicone rubber, EEW=300

TABLE 13 Viscosity (CPS) at ambient conditions (23° C./50% RH) C16 17 1819 20 21 22 23 comp A >1000 850 810 700 930 >1000 950 >1000 comp. A + B720 600 560 490 640 680 620 740

TABLE 14 Pot life at 23° C./50% RH C16 17 18 19 20 21 22 23 Pot 60 75 75120 100 95 105 120 life [min] *comparative

Increasing amount of hydrocarbon resin leads to an increased potlife.

Increasing amounts of Epodil LV5 reduces the viscosity in both Comp. Aand in the mixture of comp. A+Comp B.

Epodil Lv-5 seems to give more effect than other hydrocarbon resins.Novares LR600 (Recipe 8) was closest in viscosity reduction.

The invention claimed is:
 1. An ultra-high solids content primer coatingcomposition comprising: (i) 5.0 to 50 wt %, based on the total weight ofthe composition, of at least one bisphenol F epoxy resin; (ii) 1.5 to 12wt %, based on the total weight of the composition, of at least onesilane; (iii) 0 to 20 wt %, based on the total weight of thecomposition, of at least one hydrocarbon resin; (iv) 1.0 to 15 wt %,based on the total weight of the composition, of at least one reactivediluent; and (v) at least one curing agent; wherein said composition hasa solids content of at least 90 wt % measured according to ASTMD5201-05; wherein said composition has a viscosity of 200 to 800 cps at23° C. and 50% RH (ASTM D4287); wherein the ratio between activehydrogen equivalents in the at least one curing agent and epoxyequivalents of the coating composition is in the range 50:100 to120:100; and wherein the ultra-high solids content primer coatingcomposition has a pot life at 23° C. of more than 70 minutes.
 2. Thecoating composition as claimed in claim 1, wherein the compositioncomprises 0.5 to 20 wt %, based on the total weight of the composition,of the at least one hydrocarbon resin (iii).
 3. The coating compositionas claimed in claim 1 wherein said composition has viscosity of 300-600cps at 5° C., 50% RH.
 4. The coating composition as claimed in claim 1wherein the at least one bisphenol F epoxy resin (i) has an epoxyequivalent weight of 300 or less.
 5. The coating composition as claimedin claim 1 wherein the at least one silane (ii) is an epoxy functionalsilane.
 6. The coating composition as claimed in claim 1 wherein saidcomposition has a solvent content of less than 5 wt %.
 7. The coatingcomposition as claimed in claim 1, wherein the composition comprises 2.0to 10 wt %, based on the total weight of the composition, of the atleast one silane (ii).
 8. The coating composition as claimed in claim 1wherein the at least one reactive diluent (iv) is 1,6-hexanedioldiglycidyl ether or 1,4-butanediol diglycidyl ether.
 9. The coatingcomposition as claimed in claim 1 wherein coating composition has asolids content of at least 95%.
 10. The coating composition as claimedin claim 1 wherein the at least one curing agent (v) is phenalkamine ora polyamine curing agent.
 11. The coating composition as claimed inclaim 1 wherein the at least one reactive diluent (iv) has a viscosityof 50 cPs or less.
 12. The coating composition as claimed in claim 1wherein the at least one reactive diluent (iv) is a difunctionalaliphatic reactive diluent.
 13. The coating composition as claimed inclaim 1 having a cone and plate viscosity below 500 cPs measured at 23°C.
 14. The coating composition as claimed in claim 1 having a VOC of 100g/L or less.
 15. The coating composition as claimed in claim 1, whereinthe composition comprises 2 to 10 wt %, based on the total weight of thecoating composition, of the at least one hydrocarbon resin (iii). 16.The coating composition as claimed in claim 1 wherein the at least onesilane (ii) is GLYMO.
 17. A kit for forming the coating composition asclaimed in claim 1 comprising a component (A) and a component (B);wherein the contents of the coating composition are present in eithercomponent (A) or component (B); wherein component (A) comprises the atleast one bisphenol F epoxy resin (i), the at least one silane (ii),optionally the at least one hydrocarbon (iii), and the at least onereactive diluent (iv); wherein component (B) comprises the at least onecuring agent (v); and wherein (i), (ii), (iii), and (iv) are present incomponent (A) and (v) is present in component (B) in amounts yieldingthe coating composition containing 5.0 to 50 wt % of (i), 1.5 to 12 wt %of (ii), 0 to 20 wt % of (iii), and 1.0 to 15 wt % of (iv), based on thetotal weight of the composition, along with the ratio of active hydrogenequivalents to epoxy equivalents of 50:100 to 120:100.
 18. The kit asclaimed in claim 17 wherein the at least one hydrocarbon resin (iii)comprises the reaction product of formaldehyde with 1,3-dimethylbenzene.19. The kit as claimed in claim 17, wherein the at least one hydrocarbon(iii) is present in component (A).
 20. A metal substrate having coatedthereon the coating composition as claimed in claim 1.